Dynamo



(No Model.)

W. H. ELKI-NS. 'DYNAMO.

No. 470,785. Patented Mar. 15, 1892.

PATENT OFFICE,

\VILLIAM H. ELKINS, OF CAMBRIDGE, MASSACHUSETTS.

DYNAMO.

SPECIFICATION forming part of Letters Patent N 0. 470,785, dated March 15, 1892.

Application filed July 11, 1891' Serial No. 399,235. (No model.)

To all whom it may concern.-

Be it known that I, YVILLIAM HENRY EL- KINS, of Cambridge, in the county of MiddleseX and State of Massachusetts, have invented an Improvement in Dynamos, of which the following is a specification, reference being had to the accompanying drawing, which isa diagram illustrating my invention.

In my patent, No. 460,372, dated September 29, 1801, application filed November 28,1890, I have described a dynamo the current in which is kept constant by dividing the circuit into two portions and carrying one of these portions through a part of the field-coil. My present invention relates to dynamos constructed on the principle described in that patent; and it consists in a dynamo with two pairs of brushes, one brush of the positive pair connected to the positive terminal of a circuit of which a portion of the field-coil and translating devices form a part, and the corresponding brush of the negative pair connected to the negative terminal of that circuit, the other brushes of the positive and negative pairs being connected, respectively, to the positive and negative terminals through portions of the field-coil, which always carry less'current than those portions of the fieldcoil which carry the same current as the translatiug devices, the numberof turns of wirein those portions of the field-coil with the smaller current being so proportioned to the number of turns of wire in the corresponding portions with the constant current as to produce equality of ampere-turns at full load, notwithstanding the reduced current in the regulating portions of the coil and the constant current in the other portions of the coil.

B indicates the comm utator; B, the armature, and D D a positive and negative brush connected with the terminals T T of the circuit which includes portions A A of the fieldcoil and the translating devices. The other brushes D D connect, respectively, with the terminals T and T through the coils A and A and the number of turns of wire in these coils A and A is such with relation to the number of turns in the coils A A that while, say, ten amperes through coils A A will give a certain number of ampere-turns half that number of amperes through coils A A will give the same number of ampere-turns. These figures are taken for the reason that the brushes may be so adjusted that if ten amperes be assumed as the current desired in the Work-circuit five will flow through brushes .D and D" and five through brushes D and D making ten through the work-circuit and coils AA, but only five through coils A A Hence coils A A in this example of my invention, will comprise twice as many turns as do the coils A A; therefore the total number of ampere-turns which is suitable for full load.

On any decrease of resistance in the work circuit (as by cutting out one or more lamps) the current in that circuit wouldinstantlyincrease were it not that the diameter of commutation shifts, thereby increasing the current through D and D and decreasing the current through D and D and also decreasing the number of ampere-turns energizing pole S. This so weakens the field that the total current remains nearly constant. Conversely, when the dynamo is running at a minimum load, any increase of resistance in the work-circuit (as by introducing one or more lamps) would tend to instantly decrease the current in that circuit were it not that the diameter of commutation shifts in such a way as to decrease the current through D and D and increase the current through D and D which increases the ampere-turns energizing pole S, and so strengthens the whole field as to keep the current substantially c011- stant.

Of course an ammeteror its equivalent will be used in practice in the usual way, and proper appliances, either worked by hand or automatic, may also be used to more closely regulate the current; but these are matters so familiar to all skilled in the art that they need no description.

\Vhat I claim as my invention is- In a constant-current dynamo, two pairs of brushes of like sign, as D D and D D one brush of each pair, as D, connected to the corresponding brush of the other pair, as D, by a circuit of which portions A A of the fieldcoils and translating devices form a part, the

other two brushes of each pair, as D and D connected to the terminals T T of that circuit through other portions A A of the fieldcoils, the constant current at full load flowing through the main coils A A and a smaller current flowing through the regulating-coils A A and the number of turns of Wire in the regulating-coils being materially greater than the nuinber of turns in the corresponding portions of the main coils, all substantially as described.

NV. H. ELKINS.

Witnesses: I

J. E. MAYNADIER, EDWARD S. BEACH. 

